Haze Inside Baader Hershel Wedge

I have a fairly new wedge and have been seeing a faint black round spot in the eyepiece when viewing the sun. I didn't see it while viewing the moon with the same eyepieces so I wondered if it was something in the wedge.

When inside the house I took the wedge apart to look inside. There was not much dust because the wedge is quite new. But I noticed a haze under the top piece of glass.

Some of you might recall I started a thread a few weeks ago about smoke from my wedge. When I tried it for the 1st time with my Tec 160FL there was smoke coming from it. I contacted Astro Physics where I purchased it and they said they hadn't seen it before but there could be something that could be burned off. So I used it a few more times and it no longer produces smoke. But now I wonder if this haze is a result of that smoke. If anyone has the time I would greatly appreciate it if you could look inside your wedge using a bright light so you can see below the top piece of glass to see if you see any hazing. I want to know if that is normal or not. It doesn't seem like it should be but you never know.

I have the older version of this unit but I have no sign of hazing or smoking, and I bought mine brand new as well. When you say you are seeing hazing, exactly where is it, on the entrance side or the exit side? The entrance side is the side that goes into the focuser while the exit side is that of the eyepiece. If it is the exit side, do you have the photographic or the visual version of the wedge? If the visual version, is the ND filter glued in in some manner or can the ND and solar continuum filter both be removed? What I am trying to determine by asking this is which surface you are seeing the hazing on, the prism itself, or on the back or front of (a possibly fixed in place) ND filter. In either case I would think that you might want to get it checked out and would give AP another call.

I don't know how the haze would be the cause of the dark spot. Is it centered? Have you switched eyes by moving from left eye to right eye without turning your head? Does the dark spot also switch sides by following the eye used? It could be your blind spot where the optic nerve attaches to the eye. The blind spot is (visually) to the right of center on the right eye and left of center on the left eye.

Thanks for your help, M13. I see the haze on what I think is a piece of glass under the top glass within the wedge itself. Therefore I don't have access to it because there is one piece of glass and then something underneath before the ceramic plate and it is completely covered in a smoky haze. The ND filter and Continuum filters are removed and so is the "neck" part that goes into the focuser so that I could get a good look inside. I have the photo version. Yes I may have to return the wedge. I will get info here first and then contact AP.

Yes I doubt the dark spot is caused by the haze but that is what got me looking in the first place. The spot does seem perfectly centered and round. Yes I have switched eyes and the spot remains. Someone else mentioned my blind spot in the eyepiece forum.

I am at a loss as to the second piece of glass in there. I don't think there is one. You should be looking directly into the prism from either end if the filters have been removed. At least, this is the case with mine but the new one may very well be different. Looking in either direction into mine does not look smoky/hazy but it sure cuts down the amount of light reflected out. Could be that the front surface of yours has been coated with a haze of the smoke / burnt oil and it should definitely be cleaned.

As to the central darkening, I don't know. Maybe add in another ND filter to the ND stack to drop the light intensity a bit more and see if that changes things. It could be a visual perception thing. Do you have anyone else you could drag over to have a look to confirm the central darkening?

Thanks again for all the ideas. Perhaps there is not a 2nd piece of glass in the prism but it looks as though it is under the top of the exposed glass. I see a little dust on top of this glass and then the haze appears further down. Maybe it is on the bottom of this glass. I could try to use a micro fiber cloth to see if anything comes off but I looked at several different angles and it sure appeared under that top exposed surface. I can look again some time. I don't have it here with me now.

Good idea about getting someone else to check for the dark spot. I have some young children who can help me with this when I get it set up again. I looked at the moon and I could not see the spot with the same EP but I will try it again sometime and look more closely on a part of the moon without too many craters.

I am at home now so checked out the inside of the prism again. It looks like a "see-through" mirror on top. I don't see the haze when looking through the EP end. But looking through the focuser end I can see the ceramic tile at the bottom but below the top surface of the mirror is the haze. It looks like the haze is under the mirror but I have not tried anything because I want to contact AP first. If I look at the hazing up close it looks like it has a very small bubbling texture so I am not sure if it is removable with a cloth. Perhaps this is what was burning. Maybe there is a coating of something that burned. I am going to contact AP to see what they say. Thanks.

It's not a mirror per-se. It's a prism. From the focuser end you may be seeing something on the back side of the prism. At the eyepiece end you see only the uncoated first surface reflection from the front side of the prism. 4.6% of the light is reflected towards the eyepiece end. The rest of the light goes out the back of the prism.

I have heard back from AP. AP contacted Baader and they have never seen anything like it before so AP would like me to send the wedge back to them so they can send it to Baader to look at. From what I have heard from others this process could take months. I am not sure what to do. I want my wedge to be a good one but I wish they would just replace it so I wouldn't have to be without it for months. I may have to buy a new one and then sell the fixed one (as fixed) once I get it back. Maybe in the end they will replace it but I won't know for quite some time.

Another update. I decided to order another wedge so that I could return this one and not be without for months. I looked at this new one and there was no hazing. I tried it out today and this one smoked too and then also left a haze. It stopped smoking after a while just like the first. So I think I won't send it to Baader since even if he sent me a new one it would probably do the same thing. I will keep it because I don't believe the hazing affects the view much if at all. Can't be sure on that unless I did extensive side by side testing with a new unaffected one and that is too late now and would be difficult to do since it smokes immediately. Thanks for listening. Kent

160mm refractor, maybe ill just MAIL you the filters to test on that skymonster

I live in Flagstaff, AZ so lots of sun here. Your filter looks really good. And thanks for the generous offer. Unfortunately I don’t have the time to be fiddling with too many new projects right now. I wish I did but I am lucky to get a little observing now and then and taking care of this wedge problem has taken a lot longer than I had hoped. Thanks again though.